The metabolic effects of several biliary radiocontrast media (RCM) on the enzymes involved in both phases of drug metabolism will be studied in experimental animals. Among the enzymes to be investigated are UDP-Glucuronyl Transferase (UDPGT) and the cytochrome P450 of liver microsomes. The possible metabolities of RCM formed by the action of the drug metabolizing enzymes will be isolated and characterized by a variety of techniques and their effects on the metabolism of other substrates will be studies on isolated microsomal preparations. The possible "in vivo" effects of these compounds on the induction of UDPGT and P450 system by different agents will also be studied. Potential mutagenic effects of the PCM and their metabolites will be investigated as part of this study.